Effect of water and methanol solvents on the properties of CuO thin films deposited by spray pyrolysis

Highlights: • CuO thin films deposited by spray pyrolysis method using water or methanol as solvent. • Solvent effect on the properties of CuO thin films studied. • Formation of CuO monoclinic phase demonstrated. • Dense interconnected morphologies and different film thickness obtained. • Lower transmittance of CuO prepared from aqueous solution compared to methanolic one. -- Abstract: We report on the effect of using different solvents, water and methanol, on the structural, morphological and optical properties of CuO thin films prepared by the spray pyrolysis method. Two samples have been deposited onto low price glass substrates at 480 °C and characterized by means of X-ray diffraction, micro-Raman, scanning electron microscopy and UV–Vis spectrophotometry. The X-ray diffraction study reveals characteristic peaks assigned to CuO monoclinic phase for both samples. The same phase is confirmed by micro-Raman analysis. The surface morphology of CuO thin film prepared with distilled water as solvent presents a dense structure with particle sizes in the 40–160 nm range, while that of the sample prepared using methanol as solvent shows inter-connected grains with isolated pores and indistinguishable grain boundaries. UV–Vis spectroscopy analysis shows that the thinner sample (110 nm) obtained from methanolic solution is more transparent than the thicker one (208 nm) prepared from aqueous solution. The estimated optical band gaps are 2.18 and 2.13 eV for the samples prepared with methanol and water, respectively.